The demand for mobile data and voice communication continues to evidence significant growth. Examples for mobile communication systems include cellular-based wireless communication networks. Such networks include various network nodes. The network nodes may include base stations which respectively provide coverage for a radio cell.
A user equipment of a mobile communication network may be a Proximity Service (ProSe) enabled device. Several ProSe enabled user equipments which are located in proximity to each other are operative to perform device-to-device (D2D) communication. D2D communication allows user equipments of a mobile communication network to directly communicate with each other when the user equipments are located in proximity to each other. D2D communication has a wide variety of applications, including public safety and other use cases. Emergency calls are one example for public safety use cases of D2D communication. Direct data or voice communication between user equipments is another example for use cases of D2D communication. For illustration, ProSe enabled user equipments located in proximity to each other may engage in data or voice communication.
In order to perform D2D communication, a user equipment must be capable of detecting one or several other user equipments which are located in proximity to the user equipment. The resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the D2D discovery may be allocated to the user equipment by a base station. Similarly, the resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the D2D communication may be allocated to the user equipment by a base station.
Various techniques may be used for allocating resources for D2D discovery and/or D2D communication. The base station may allocate resources for the D2D discovery and/or for the D2D communication in a manner which is not specific to a particular user equipment, e.g. by broadcasting the information on the allocated resources to a group of user equipments. In the art, this technique is also referred to as allocation of “type 1 D2D discovery resources”. D2D discovery resources allocated in a manner which is not specific for a user equipment are also referred to as “type 1 D2D discovery resources” in the art.
At least for some use cases, it is attractive to allocate resources on a per-user-equipment basis. I.e., the D2D resources are allocated specifically to each user equipment. Examples for such use cases are D2D discovery and communication at advertisement points, e.g. at a mall or a retail shop, D2D discovery and communication at vending machines, or other commercial or public safety use cases. The specific allocation of resources may also be attractive to accommodate different service types or public safety use cases. In the art, this technique is also referred to as allocation of “type 2 D2D discovery resources”. D2D discovery resources allocated in a manner which is specific for a user equipment are also referred to as “type 2 D2D discovery resources” in the art.
It may be difficult for the network side, e.g. the EUTRAN network, to keep track of the usage of resources and network loads for D2D discovery. As one example, when every user equipment can decide autonomously when to start using the allocated type 1 D2D discovery resources, the resources actually used for the D2D discovery and/or communication may become too high and it may be challenging to accommodate the needs of D2D discovery which should be prioritized, e.g. for public safety reasons. A dedicated signaling for authorizing the usage of D2D discovery resources may significantly increase the network loads and communication overheads if it is performed with every ProSe enabled user equipment located in the cell.